Method for reducing elemental sulfur in gypsum products

Abstract

Disclosed are various methods for reducing levels of elemental sulfur within gypsum products such as wall board. Gypsum sometimes includes increased levels of elemental sulfur. Such sulfur can be corrosive and otherwise harmful at elevated levels. The disclosure contemplates reacting the elemental sulfur with copper to copper sulfide. This reaction has the benefit of reducing the levels of elemental sulfur present within the final gypsum product. The copper can be added at any of a variety of locations in the manufacturing process. This is a very efficient method for reducing elemental sulfur in the production of gypsum products.

What is claimed is: 
     
       1. A method for reducing of presence of elemental sulfur in a gypsum product, the method comprising the following steps:
 providing stucco to be used in the production of the gypsum product, the stucco including a level of elemental sulfur; 
 mixing copper into the stucco; 
 allowing the copper to react with the elemental sulfur, the reaction reducing the level of elemental sulfur within the stucco; 
 utilizing the stucco with the reduced level of elemental sulfur in the production of gypsum product. 
 
     
     
       2. The method as described in  claim 1  wherein the reaction between the copper and the elemental sulfur produces copper sulfide (Cu 2 S). 
     
     
       3. The method as described in  claim 1  wherein the reaction between the copper and elemental sulfur produces copper monosulfide (CuS). 
     
     
       4. The method as described in  claim 1  wherein the reaction between the copper and elemental sulfur produces copper disulfide (CuS 2 ). 
     
     
       5. The method as described in  claim 1  wherein the level of elemental sulfur within the gypsum following the reaction is below that described in ASTM C1396M-14a. 
     
     
       6. A method for reducing elemental sulfur in a gypsum product, the method comprising the following steps:
 forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSO 4  ½ H 2 O) and water, the gypsum slurry also including an amount of elemental sulfur; 
 mixing an amount of fine copper powder into the gypsum slurry; 
 allowing the copper to react with the elemental sulfur within the gypsum slurry, the reaction producing copper sulfide (Cu 2 S); 
 the production of the copper sulfide (Cu 2 S) reducing the amount of elemental sulfur present in the gypsum slurry; 
 utilizing the gypsum slurry in the production of the gypsum product. 
 
     
     
       7. The method as described in  claim 6  wherein the slurry includes a starch and a retarder. 
     
     
       8. The method as described in  claim 6  wherein the slurry further comprises one or more of the following: foam, wax, glass fibers, and sugars. 
     
     
       9. The method as described in  claim 6  wherein the level of elemental sulfur within the gypsum following the reaction is below that described in ASTM C1396M-14a. 
     
     
       10. The method as described in  claim 6  wherein the gypsum product is a wall board. 
     
     
       11. A method for reducing elemental sulfur in gypsum wallboard, the method comprising the following steps:
 providing a volume of calcium sulfate dihydrate (CaSO 4  2H 2 O) containing an amount of elemental sulfur; 
 crushing the calcium sulfate dihydrate (CaSO 4  2H 2 O) in a mill; 
 heating and calcining the crushed calcium sulfate dihydrate (CaSO 4  2H 2 O) to produce calcium sulfate hemihydrate (CaSO 4  ½ H 2 O), the calcium sulfate hemihydrate (CaSO 4  ½ H 2 O) containing an amount of elemental sulfur; 
 mixing an amount of fine copper powder with the calcium sulfate hemihydrate (CaSO 4  ½ H 2 O), with the weight ratio between the fine copper powder and the elemental sulfur in the gypsum being in the range of approximately 1 to 1 to approximately 4 to 1; 
 allowing the copper to react with the elemental sulfur within the heated calcium sulfate hemihydrate (CaSO 4  ½ H 2 O), the reaction producing copper sulfide (Cu 2 S); 
 the production of the copper sulfide (Cu 2 S) reducing the amount of elemental sulfur (S) present in the calcium sulfate hemihydrate (CaSO 4  ½ H 2 O); 
 utilizing the calcium sulfate hemihydrate (CaSO 4  ½ H 2 O) in the production of gypsum wallboard. 
 
     
     
       12. The method as described in  claim 11  wherein the method further comprises the step of collecting ground fines and wherein the copper powder is added after the ground fines are collected. 
     
     
       13. The method as described in  claim 11  wherein zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), or Cobalt (Co) are used in place of the copper powder (Cu). 
     
     
       14. The method as described in  claim 11  wherein metallic oxides are used in place of the copper powder. 
     
     
       15. The method as described in  claim 11  wherein the copper powder is added to the gypsum feed stream. 
     
     
       16. The method as described in  claim 11  wherein the copper powder is added immediately after the formation of a stucco slurry. 
     
     
       17. The method as described in  claim 11  wherein the copper powder is directly added after calcination. 
     
     
       18. The method as described in  claim 11  wherein the copper powder is added via a stucco feed stream. 
     
     
       19. The method as described in  claim 11  wherein a board dryer is used to increase the efficiency of the reaction between the copper and the elemental sulfur. 
     
     
       20. The method as described in  claim 11  wherein the efficiency of the reaction between the copper and the elemental sulfur is increased via residence times within a silo. 
     
     
       21. The method as described in  claim 11  wherein the weight ratio between the fine copper powder and the elemental sulfur in the gypsum is in the range of approximately 1 to 1 to approximately 4 to 1. 
     
     
       22. The method as described in  claim 11  wherein the copper powder is added to the calciner feed stream. 
     
     
       23. A method for producing a gypsum product with enhanced physical properties, the method comprising:
 providing a volume of gypsum, the gypsum containing an amount of elemental sulfur; 
 mixing an amount of copper powder with the gypsum; 
 allowing the copper to react with the elemental sulfur in the gypsum; 
 utilizing the gypsum in the production of the gypsum product. 
 
     
     
       24. The method as described in  claim 23  wherein the amount of added copper is greater than 500 ppm and the enhanced physical property in the gypsum product is inhibited mold and mildew growth. 
     
     
       25. The method as described in  claim 23  wherein copper is added in range of approximately 20 ppm to approximately 1000 ppm and the enhanced physical property in the gypsum product is inhibited mold and mildew growth. 
     
     
       26. The method as described in  claim 23  comprising the further step of calcining the gypsum and wherein the step of mixing the copper powder is carried out before the calcining step. 
     
     
       27. The method as described in  claim 23  comprising the further step of calcining the gypsum and wherein the step of mixing the copper powder is carried out after the calcining step.